Projection devices are utilized in a variety of settings. These devices include video production equipment, motion picture projection equipment and lens projection systems. Typically, these devices are utilized to produce full-color single perspective (i.e., two-dimensional) images. However, in some applications it is desirable to generate images that provide the illusion of depth or relief images. That is, in some instances it is desirable to generate images that appear three-dimensional.
Video production equipment and motion picture projection equipment can be utilized to produce full-color three-dimensional relief images. However, these three-dimensional systems are typically large, complex and expensive. Accordingly, these systems are not well suited for applications such as advertising or generating background images for use in theater or concert settings. In contrast, lens projection systems, which utilize a light source to project a light beam through a projection mask and one or more lens, are typically compact, mechanically simple and relatively inexpensive. These projection masks are generally partially translucent slides or silhouette type images.
While lens projection systems are well suited for many applications, difficulty arises in utilizing these systems to generate three-dimensional relief images. However, in some instances, lens projection systems may be adapted generate three-dimensional relief images. For example, stereoscopic projection systems project pairs of individual picture elements having separate perspectives corresponding to the perspective offered by the right and left eyes of a viewer. The individual picture elements are generally taken from two different points of view and each eye of the viewer receives only the information obtained from one point of view when viewing the projected images on a screen. Accordingly, viewers may have to wear specialized glasses to view such images. In any case, such stereoscopic projection systems require multiple projection units and/or multiple perspective views of an image to generate a three-dimensional relief image and are accordingly complex and expensive.
Other lens projection systems have been adapted to provide an illusion of depth from a single projected image obtained from only one point of view. Such systems often utilize optical separators to separate light from a light source into a number of individual light bands. Optical generators may also be utilized to generate a plurality of optical images from the individual light bands, which may then be recombined to form a single image. Re-combination typically involves utilizing polarizing filters in order to shift one or more light bands, oriented in a first direction, relative to other light bands, that may be oriented in other directions, such that the illusion of depth is created in the recombined image. These systems typically rely upon complex electronics and polarizing light filters that result in images that have reduced brightness and/or clarity as well as poor color contrast. Again, these systems tend to be complex and for many applications prohibitively expensive.